Re: O_DIRECT support for Windows

> People seem to be confusing sector size and cluster size.
>
> Microsoft Windows assumes sectors are 8k or less on hard drives (99% are
> 512 bytes).

Do you have any doc ref for this? I beleive you but I've been searching for docs on that and found nothing.

>
> Cluster size is the allocation unit.  On windows, this can be 512 to
> 256k (max 64k with 512 byte sectors).
> NTFS (which I think we need) is limited to 64k, last I looked.

Correct.


> On RAID devices, the allocation unit might actually be larger, but
> usually the *sector* size of these devices is still 8k or less (usually,
> they mimic the 512 byte sector size, because too much software assumes
> this)

Usually being the thing that might require an extra check.

> And that restriction is only for certain drivers and devices.  Many
> don't enforce the restriction.
> But to be safe, sector alignment is best, because there are some drivers
> that care.

exactly. so we need that check to be sure, don't we?

/Magnus